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   /*
    * Copyright 2017 The Netty Project
    *
    * The Netty Project licenses this file to you under the Apache License,
    * version 2.0 (the "License"); you may not use this file except in compliance
    * with the License. You may obtain a copy of the License at:
    *
    *   https://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   * License for the specific language governing permissions and limitations
   * under the License.
   */
  package io.netty.handler.codec.http2;
  
  import io.netty.channel.Channel;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelHandler;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelOption;
  import io.netty.channel.ChannelPipeline;
  import io.netty.util.AttributeKey;
  import io.netty.util.concurrent.EventExecutor;
  import io.netty.util.concurrent.Future;
  import io.netty.util.concurrent.Promise;
  import io.netty.util.internal.ObjectUtil;
  import io.netty.util.internal.StringUtil;
  import io.netty.util.internal.UnstableApi;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.nio.channels.ClosedChannelException;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  @UnstableApi
  public final class Http2StreamChannelBootstrap {
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(Http2StreamChannelBootstrap.class);
      @SuppressWarnings("unchecked")
      private static final Map.Entry<ChannelOption<?>, Object>[] EMPTY_OPTION_ARRAY = new Map.Entry[0];
      @SuppressWarnings("unchecked")
      private static final Map.Entry<AttributeKey<?>, Object>[] EMPTY_ATTRIBUTE_ARRAY = new Map.Entry[0];
  
      // The order in which ChannelOptions are applied is important they may depend on each other for validation
      // purposes.
      private final Map<ChannelOption<?>, Object> options = new LinkedHashMap<ChannelOption<?>, Object>();
      private final Map<AttributeKey<?>, Object> attrs = new ConcurrentHashMap<AttributeKey<?>, Object>();
      private final Channel channel;
      private volatile ChannelHandler handler;
  
      // Cache the ChannelHandlerContext to speed up open(...) operations.
      private volatile ChannelHandlerContext multiplexCtx;
  
      public Http2StreamChannelBootstrap(Channel channel) {
          this.channel = ObjectUtil.checkNotNull(channel, "channel");
      }
  
      /**
       * Allow to specify a {@link ChannelOption} which is used for the {@link Http2StreamChannel} instances once they got
       * created. Use a value of {@code null} to remove a previous set {@link ChannelOption}.
       */
      public <T> Http2StreamChannelBootstrap option(ChannelOption<T> option, T value) {
          ObjectUtil.checkNotNull(option, "option");
  
          synchronized (options) {
              if (value == null) {
                  options.remove(option);
              } else {
                  options.put(option, value);
              }
          }
          return this;
      }
  
      /**
       * Allow to specify an initial attribute of the newly created {@link Http2StreamChannel}.  If the {@code value} is
       * {@code null}, the attribute of the specified {@code key} is removed.
       */
      public <T> Http2StreamChannelBootstrap attr(AttributeKey<T> key, T value) {
          ObjectUtil.checkNotNull(key, "key");
          if (value == null) {
              attrs.remove(key);
          } else {
              attrs.put(key, value);
          }
          return this;
      }
  
      /**
       * the {@link ChannelHandler} to use for serving the requests.
       */
      public Http2StreamChannelBootstrap handler(ChannelHandler handler) {
          this.handler = ObjectUtil.checkNotNull(handler, "handler");
          return this;
      }
 
     /**
      * Open a new {@link Http2StreamChannel} to use.
      * @return the {@link Future} that will be notified once the channel was opened successfully or it failed.
      */
     public Future<Http2StreamChannel> open() {
         return open(channel.eventLoop().<Http2StreamChannel>newPromise());
     }
 
     /**
      * Open a new {@link Http2StreamChannel} to use and notifies the given {@link Promise}.
      * @return the {@link Future} that will be notified once the channel was opened successfully or it failed.
      */
     public Future<Http2StreamChannel> open(final Promise<Http2StreamChannel> promise) {
         try {
             ChannelHandlerContext ctx = findCtx();
             EventExecutor executor = ctx.executor();
             if (executor.inEventLoop()) {
                 open0(ctx, promise);
             } else {
                 final ChannelHandlerContext finalCtx = ctx;
                 executor.execute(new Runnable() {
                     @Override
                     public void run() {
                         if (channel.isActive()) {
                             open0(finalCtx, promise);
                         } else {
                             promise.setFailure(new ClosedChannelException());
                         }
                     }
                 });
             }
         } catch (Throwable cause) {
             promise.setFailure(cause);
         }
         return promise;
     }
 
     @SuppressWarnings("deprecation")
     private ChannelHandlerContext findCtx() throws ClosedChannelException {
         // First try to use cached context and if this not work lets try to lookup the context.
         ChannelHandlerContext ctx = multiplexCtx;
         if (ctx != null && !ctx.isRemoved()) {
             return ctx;
         }
         ChannelPipeline pipeline = channel.pipeline();
         ctx = pipeline.context(Http2MultiplexCodec.class);
         if (ctx == null) {
             ctx = pipeline.context(Http2MultiplexHandler.class);
         }
         if (ctx == null) {
             if (channel.isActive()) {
                 throw new IllegalStateException(StringUtil.simpleClassName(Http2MultiplexCodec.class) + " or "
                         + StringUtil.simpleClassName(Http2MultiplexHandler.class)
                         + " must be in the ChannelPipeline of Channel " + channel);
             } else {
                 throw new ClosedChannelException();
             }
         }
         multiplexCtx = ctx;
         return ctx;
     }
 
     /**
      * @deprecated should not be used directly. Use {@link #open()} or {@link #open(Promise)}
      */
     @Deprecated
     public void open0(ChannelHandlerContext ctx, final Promise<Http2StreamChannel> promise) {
         assert ctx.executor().inEventLoop();
         if (!promise.setUncancellable()) {
             return;
         }
         final Http2StreamChannel streamChannel;
         try {
             if (ctx.handler() instanceof Http2MultiplexCodec) {
                 streamChannel = ((Http2MultiplexCodec) ctx.handler()).newOutboundStream();
             } else {
                 streamChannel = ((Http2MultiplexHandler) ctx.handler()).newOutboundStream();
             }
         } catch (Exception e) {
             promise.setFailure(e);
             return;
         }
         try {
             init(streamChannel);
         } catch (Exception e) {
             streamChannel.unsafe().closeForcibly();
             promise.setFailure(e);
             return;
         }
 
         ChannelFuture future = ctx.channel().eventLoop().register(streamChannel);
         future.addListener(new ChannelFutureListener() {
             @Override
             public void operationComplete(ChannelFuture future) {
                 if (future.isSuccess()) {
                     promise.setSuccess(streamChannel);
                 } else if (future.isCancelled()) {
                     promise.cancel(false);
                 } else {
                     if (streamChannel.isRegistered()) {
                         streamChannel.close();
                     } else {
                         streamChannel.unsafe().closeForcibly();
                     }
 
                     promise.setFailure(future.cause());
                 }
             }
         });
     }
 
     private void init(Channel channel) {
         ChannelPipeline p = channel.pipeline();
         ChannelHandler handler = this.handler;
         if (handler != null) {
             p.addLast(handler);
         }
         final Map.Entry<ChannelOption<?>, Object> [] optionArray;
         synchronized (options) {
             optionArray = options.entrySet().toArray(EMPTY_OPTION_ARRAY);
         }
 
         setChannelOptions(channel, optionArray);
         setAttributes(channel, attrs.entrySet().toArray(EMPTY_ATTRIBUTE_ARRAY));
     }
 
     private static void setChannelOptions(
             Channel channel, Map.Entry<ChannelOption<?>, Object>[] options) {
         for (Map.Entry<ChannelOption<?>, Object> e: options) {
             setChannelOption(channel, e.getKey(), e.getValue());
         }
     }
 
     private static void setChannelOption(
             Channel channel, ChannelOption<?> option, Object value) {
         try {
             @SuppressWarnings("unchecked")
             ChannelOption<Object> opt = (ChannelOption<Object>) option;
             if (!channel.config().setOption(opt, value)) {
                 logger.warn("Unknown channel option '{}' for channel '{}'", option, channel);
             }
         } catch (Throwable t) {
             logger.warn(
                     "Failed to set channel option '{}' with value '{}' for channel '{}'", option, value, channel, t);
         }
     }
 
     private static void setAttributes(
             Channel channel, Map.Entry<AttributeKey<?>, Object>[] options) {
         for (Map.Entry<AttributeKey<?>, Object> e: options) {
             @SuppressWarnings("unchecked")
             AttributeKey<Object> key = (AttributeKey<Object>) e.getKey();
             channel.attr(key).set(e.getValue());
         }
     }
 }